Eggshell color in brown-egg laying hens - a review

Area of Science:

• Poultry Science
• Animal Biochemistry
• Egg Quality

Background:

• Brown eggshells primarily contain protoporphyrin IX, with traces of biliverdin and its zinc chelates.
• The synthesis of eggshell pigment occurs in the shell gland, though the exact mechanisms remain unclear.
• While the protoporphyrin IX pathway is known, its specific synthesis and genetic control in brown-egg layers require further understanding.

Purpose of the Study:

• To review the physiological and biochemical characteristics of brown eggshell pigment.
• To explore the synthesis and deposition of protoporphyrin IX in commercial laying hens.
• To discuss the factors influencing brown eggshell coloration and its significance in the poultry industry.

Main Methods:

• Literature review of physiological and biochemical studies on eggshell pigments.
• Analysis of research on the protoporphyrin IX synthetic pathway.
• Examination of factors affecting pigment deposition in commercial laying hens.

Main Results:

• Protoporphyrin IX is the major brown pigment, synthesized in the shell gland and deposited across shell layers, concentrated in the outer calcareous layer and cuticle.
• Identified genes involved in pigment synthesis, but genetic control of brown pigment synthesis and deposition is not fully elucidated.
• Eggshell brown coloration is a key quality trait influenced by housing, hen age, strain, diet, stress, and disease.

Conclusions:

• Understanding the synthesis and deposition of brown eggshell pigment is crucial for optimizing egg quality.
• Factors influencing pigment deposition highlight the complexity of genetic and environmental interactions.
• Brown eggshell color significantly impacts consumer preference and market value in the poultry industry.